(Date of issue: September 2014. Version: 2)
This factsheet has been written for members of the public by the UK Teratology Information Service (UKTIS). UKTIS is a not-for-profit organisation funded by Public Health England on behalf of UK Health Departments. UKTIS has been providing scientific information to health care providers since 1983 on the effects that medicines, recreational drugs and chemicals may have on the developing baby during pregnancy.
What is it?
Chlorphenamine (Allercalm®, Hayleve®, Piriton®, Pollenase®) is an antihistamine used to treat hay fever, skin allergies, and other allergic symptoms. It causes drowsiness and is therefore referred to as a sedating antihistamine.
Is it safe to take chlorphenamine in pregnancy?
This leaflet summarises the scientific studies relating to the effects of chlorphenamine on a baby in the womb. It is advisable to consider this information before taking chlorphenamine if you are pregnant.
There is no currently no evidence that chlorphenamine is harmful to a baby in the womb. However because only a small number of pregnant women taking chlorphenamine have been studied, it is not possible to say for certain that it does not affect a baby in some way.
When deciding whether or not to take chlorphenamine during pregnancy it is important to weigh up how necessary chlorphenamine is to your health against the possible risks to you or your baby, some of which will depend on how many weeks pregnant you are.
What if I have already taken chlorphenamine during pregnancy?
If you have taken or are taking any medicines, it is always a good idea to let your doctor know that you are pregnant so that you can decide together whether you still need the medicines that you are on and if so, to make sure that you are taking the lowest dose that works, and only for as long as you need to.
Can taking chlorphenamine in pregnancy cause birth defects in the baby?
A baby’s body and most internal organs are formed during the first 12 weeks of pregnancy. It is mainly during this time that some medicines are known to cause birth defects.
A number of studies have suggested possible links between taking chlorphenamine in early pregnancy and various specific birth defects (malformations). In some cases, other studies investigating the same birth defect have shown no link. The studies are detailed below:
• A study from many years ago suggested a possible link between chlorphenamine use in early pregnancy and having a baby with an eye or ear defect. However, this was based upon small numbers of chlorphenamine-exposed babies and a more recent study did not agree with this finding.
• One study suggested a possible link between taking chlorphenamine or a related antihistamine in early pregnancy and having a baby with spina bifida (an opening of the spine), but another study was unable to confirm this finding.
• One study suggested a possible link between taking chlorphenamine or another similar antihistamine in early pregnancy and having a baby with a cleft lip and/or palate (a split in the lip and/or the roof of the mouth), but another study found no proof of a link.
• One study from many years ago suggested a possible link between taking chlorphenamine in early pregnancy and having a baby with an inguinal hernia (an opening or ‘tunnel’ in the groin muscles that may appear as a lump under the skin if part of the bowel bulges through). This however, was based upon small numbers of chlorphenamine-exposed babies and it is therefore not possible to say that there is a link based on only one study.
• One study showed a possible link between chlorphenamine use in early pregnancy and having a baby with certain types of heart defect, however another two studies have not shown a link between chlorphenamine use in pregnancy and heart defects in the baby.
Taken together, the results of these studies do not provide firm evidence to link taking chlorphenamine during early pregnancy with any of the defects listed above. However, better scientific evidence still needs to be collected to say for certain that chlorphenamine does not cause birth defects.
Can taking chlorphenamine in pregnancy cause miscarriage?
No studies have investigated the occurrence of miscarriage in women who took chlorphenamine during pregnancy.
Two studies of pregnant women who took any type of antihistamine have both shown no increase in the risk of miscarriage. Although chlorphenamine is chemically similar to other antihistamines, it is not known whether individual antihistamines affect a pregnancy in a different way. More research is therefore needed to specifically assess whether chlorphenamine use in pregnancy affects the risk of miscarriage.
Can taking chlorphenamine in pregnancy cause preterm birth, or my baby to be small at birth (low birth weight)?
No studies have investigated the occurrence of preterm birth (before 37 weeks of pregnancy) or the chance of having a low birth weight baby (<2500g) in women who took chlorphenamine during pregnancy.
Studies of pregnant women who took any type of antihistamine have not found any links with preterm birth or low birth weight in the baby. However, we do not know how these findings relate to women specifically taking chlorphenamine and more information therefore needs to be collected from women who are taking chlorphenamine in pregnancy.
Can taking chlorphenamine in pregnancy cause stillbirth?
No studies have investigated the occurrence of stillbirth in women who took chlorphenamine during pregnancy.
Two studies have investigated whether stillbirth was more likely amongst pregnant women who took any type of antihistamine and neither found a link. However, we do not know whether chlorphenamine might affect a baby in the womb differently to other antihistamines and more research is therefore required.
Can taking chlorphenamine in pregnancy cause learning and behavioural problems in the child?
A baby’s brain continues to develop right up until the end of pregnancy. It is therefore possible that taking certain medicines at any stage of pregnancy could have a lasting effect on a child’s learning or behaviour.
There is no known link between taking chlorphenamine or antihistamines as a group during pregnancy and learning or behavioural problems (such as ADHD or autism spectrum disorder) in the child later on in life. There are however, no scientific studies that have specifically investigated links with these problems.
Will my baby need extra monitoring?
Most women will be offered a scan at around 20 weeks of pregnancy to look for birth defects as part of their routine antenatal care. Taking chlorphenamine in pregnancy would not normally require extra monitoring of your baby before birth.
Taking chlorphenamine around the time of delivery can cause withdrawal symptoms in the newborn baby, as a result of the baby’s body having to adapt to no longer getting chlorphenamine through the placenta. Close monitoring of your baby for a few days after birth may therefore be advised if you have taken chlorphenamine regularly in the weeks before delivery.
Are there any risks to my baby if the father has taken chlorphenamine?
No studies have specifically investigated whether chlorphenamine used by the father can harm the baby through affects on the sperm, however most experts agree that this is very unlikely. More research on the effects of drug and medicine use in men before and around the time of conception is needed.
Who can I talk to if I have questions?
If you have any questions regarding the information in this leaflet please discuss them with your health care provider. They can access more detailed medical and scientific information from www.uktis.org.
Up to 1 out of every 5 pregnancies ends in a miscarriage, and 1 in 40 babies are born with a birth defect. These are referred to as the background population risks. They describe the chance of these events happening for any pregnancy before taking factors such as the mother’s health during pregnancy, her lifestyle, medicines she takes and the genetic make up of her and the baby’s father into account.
Medicines use in pregnancy
Most medicines used by the mother will cross the placenta and reach the baby. Sometimes this may have beneficial effects for the baby. There are, however, some medicines that can harm a baby’s normal development. How a medicine affects a baby may depend on the stage of pregnancy when the medicine is taken. If you are on regular medication you should discuss these effects with your doctor/health care team before becoming pregnant.
If a new medicine is suggested for you during pregnancy, please ensure the doctor or health care professional treating you is aware of your pregnancy.
When deciding whether or not to use a medicine in pregnancy you need to weigh up how the medicine might improve your and/or your unborn baby’s health against any possible problems that the drug may cause. Our bumps leaflets are written to provide you with a summary of what is known about use of a specific medicine in pregnancy so that you can decide together with your health care provider what is best for you and your baby.
Every pregnancy is unique. The decision to start, stop, continue or change a prescribed medicine before or during pregnancy should be made in consultation with your health care provider. It is very helpful if you can record all your medication taken in pregnancy in your hand held maternity records.